A great variety of lawn sprinklers have been devised and manufactured. All are intended to distribute water as uniformly as possible over a given lawn area at the rate at which the water will soak into the ground. Some are simple sprinkler manifolds with no moving parts. Some provide for a multiplicity of streams from nozzles which rotate about a vertical or horizontal axis, and many are adjustable to limit the area to be sprinkled at any given setting. The constantly moving streams are preferable in that they spread the water for a given location of the sprinkler over a larger area for optimum absorption. While sprinklers rotating about a vertical axis supply water to a circular area, sprinklers which oscillate about a horizontal axis serving a rectangular area are generally preferred because the entire lawn can be uniformly watered by successively sprinkling areas with straight common boundaries. To achieve improved certainty and continuity of operation and uniform watering for a given setting, horizontal oscillating sprinklers have become increasingly complex with concomitantly increasing cost and mechanical failure probability.